That fish is called a gunnel. People mistakenly call them eels but true eels do not have pectoral fins. don't remember the scientific name at the moment. Gunnels are not common feed for salmon as they usually hide under or around rocks. This one must have been caught out in the open.

Very common in PS. Caught hundereds of them as a kid off Kayak Point County Park pier. Also, I was on a bottom trawler (sampling for contaminate) a few years ago in the Nisqually reach and they were one of the most common species collected.